In Chinese Patent No. 201220746320.8, entitled “high light efficiency light modulation apparatus and high light efficiency stereo projection system”, a large-sized polarized beam splitter device is required to split an incident light into a transmitted light beam and a reflective light beam and then adjust the polarization state of the light beams to make the two light beams overlap on a metal screen. This technology results in a long light path and hence requires large-sized optical devices. When a low throw ratio projector is used, each optical device needs to have a very large size, and overlapping of the two beams of light also becomes very difficult. In addition, there are difficulties in device manufacture and assembly as well as mass production of the projector.
What is needed, therefore, is an improved projection apparatus to overcome the above defects.